This invention relates to an antenna assembly of modular form for use in road vehicles.
For many years a single antenna was considered sufficient to satisfy the signal reception requirements of the AM/FM radio which is commonly installed in motor vehicles. In recent years additional antennas and associated diversity electronics have been introduced in order to eliminate or reduce the audio distortions that can be experienced when driving in a multipath signal environment.
As other services, such as mobile telephone (e.g, GSM) and global positioning by satellite (GPS), have been introduced, it has been necessary to add other antennas to the motor vehicle. Further services are planned which will lead to numerous other antennas also being added to the vehicle, More than twelve antenna elements could be required for the reception of existing and currently envisaged services.
The integration of so many antennas into a vehicle presents a number of problems in the design, manufacture, installation, test, servicing and upgrading phases of the product life-cycle,.
Car-designers generally impose severe constraints in terms of the allocated space, the permitted locations, the mechanical interfaces, the electrical interfaces, etc for these antennas.
For a number of years car manufacturers have provided vehicles with antennas integrated into the rear windows, so-called glass antennas, in order to offer a lower cost alternative to the more familiar external whip or telescopic mast antennas. However, the system performance obtained with these glass antennas is often compromised because the shape or form of antennas for good electrical performance is generally not compatible with the dominant aesthetic requirements. This situation is aggravated when a large number of antennas are required. Connecting tracks are used to route the signals from (or to) the glass antenna elements. Cross-over connections to these tracks are difficult to avoid and connections to screened cables and associated electronic assemblies are relatively expensive to implement reliably.
Glass antenna technology is used by the original equipment manufacturer and the antenna cannot be replaced or modified without replacing the window glass itself. Thus glass antenna technology is not appropriate for the upgrading of the antenna systems that may later be required when new services are introduced, or for the after-market.
U.S. Pat. No. 5,400,039 (Hitachi, Ltd.) discloses an integrated multi-layered microwave circuit in which conductive layers and dielectric layers are alternately laminated. A first conductive layer on one major face forms an antenna interface, and a second conductive layer on the other major face forms a circuit pattern to which discrete parts are fitted. The first and second conductive layers are connected to feed an antenna signal. Dielectric layers separate a ground layer and power source layer from each other and from the first and second conductive layers. The first conductive layer forming the antenna interface has three circular antenna radiators connected together with phase shifters.
European Patent Appln. 0 590 955 (Loral Aerospace) discloses an antenna for receiving signals in a plurality of frequency bands, and European Patent Appln. 0 806 851 (Becker GmbH) discloses that an optical data bus may be in vehicular communications.
The present invention, at least in its preferred embodiments, seeks to avoid at least some of disadvantages mentioned above. In principle, it is applicable equally to transmitting antennas and receiving antennas, and the claims are to be interpreted accordingly.
In one aspect, the invention provides an antenna module for a road vehicle comprises a structure including a plurality of antennas for receiving and/or transmitting different types of signals, and configured to be mounted in or on the vehicle, a data bus for conveying in a digital format signals received by and/or to be transmitted by the antennas between the module and equipment comprised in the vehicle, and means for converting received signals into said format and/or for converting signals to be transmitted from that format into a form for transmission.
The antennas may provide for reception and/or transmission of two or more signals of the following types: FM broadcast radio, AM broadcast radio, digital audio broadcasts, analogue broadcast television, digital broadcast television, telephony, other two-way radio communications, position fixing, station keeping, vehicle guidance, vehicle security, vehicle identification, tolling, emergency calls. xe2x80x98Broadcastxe2x80x99 includes both terrestrial and satellite transmissions, whether free-on-air or pay-to-receive.
The structure may contain active systems for signal processing before transmission or after reception.
The connection means may be adapted for conveying signals relating to vehicle security to or from the vehicle separately from other signals.
The data bus may be an optical bus.
Preferably the structure is of material substantially transparent to electromagnetic radiation.
At least one said antenna may be integrated into or disposed on the fabric of the structure.
Alternatively or in addition the structure may be a housing within which at least one said antenna is contained. The module may comprise means for mounting it on an external surface of the vehicle, and shaped to conform with the styling thereof, and/or to perform a aerodynamic function.
At least one said active system may be disposed within the housing. The module may be configured as a spoiler, fairing, airdam or fin.
At least one of the antennas may be a pattern of conductive material printed, etched or otherwise disposed on a dielectric substrate.
The module may be shaped to conform to a surface (eg. an inner surface) of a window, window surround or body panel of the vehicle.
Alternatively there may be means for mounting the module on an external surface of the vehicle, and shaped to conform with the styling thereof.
The module may be configured as a spoiler, fairing or fin for mounting towards the rear of the vehicle.